Item: INNOVATIVE HIGH-SPEED CAMERA ARRAY FOR UNPRECEDENTED INSIGHTS INTO POWDER SNOW AVALANCHES
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Title: INNOVATIVE HIGH-SPEED CAMERA ARRAY FOR UNPRECEDENTED INSIGHTS INTO POWDER SNOW AVALANCHES
Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
Authors:
- Ivan Calic [ Avalanche formation and dynamics, WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ] [ Institute of Fluid Dynamics, Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland ]
- Prof. Dr. Filippo Coletti [ Institute of Fluid Dynamics, Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland ]
- Bernhard Roth [ Institute of Fluid Dynamics, Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland ]
- Dr. Betty Sovilla [ Avalanche formation and dynamics, WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland ]
Date: 2024-09-23
Abstract: Powder snow avalanches (PSAs) pose significant threats to human lives and infrastructure in mountain regions. Measuring inside these natural flows is challenging because of their destructive power, which limits our understanding of these events. Previous research revealed a complex layering, characterized by a superposition of three distinct layers. The dense basal layer, where particle-particle interactions are dominant, is situated below two aerial layers: the suspension and transition layer, both of which are particle laden turbulent flows. In contrast to the suspension layer, the transition layer hosts a higher amount of suspended mass and intense clustering processes, resulting in high local density fluctuations. Up to now technological limitations have prevented measurements within the dilute flows, especially the inability to capture turbulence at large scales. This lack of direct observations of dilute layers complicates model development and inhibits accurate predictions of PSAs’ destructive impacts. To address this gap, we developed a non-invasive measurement technique consisting of a high-speed camera array. We installed this array on a vertical structure at the Vall ´ee de la Sionne test site in Switzerland, probing the transition and suspension layers of fully developed PSAs. The new array consists of three high-speed cameras and captures images at mm resolution from 5 m up to 11 m above ground. On December 2nd, 2023, we measured the first PSA using the new setup. The collected images show individual suspended snow particles inside the transition and suspension layers, revealing complex air-particle dynamics. With image processing algorithms, including particle image velocimetry, we extracted essential flow characteristics such as the vertical velocity profiles. This research paves the way for understanding the destructive potential of PSAs, but also lays the basis for improving prediction models and mitigation strategies. Additionally, it offers intriguing images from the inside of a PSA.
Object ID: ISSW2024_O2.2.pdf
Language of Article: English
Presenter(s): Ivan Calic
Keywords: Powder Snow Avalanche, Experimental Avalanche Dynamics, High-Speed Cameras
Page Number(s): 288 - 292
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